Automatic flushing valves are now widely used for flushing and testing water in dead ends of water systems. Examples of such systems are shown in McCarty, U.S. Pat. No. 5,921,270, Newman, U.S. Pat. Nos. 6,035,704 and 6,635,172, Taylor, U.S. Pat. Nos. 7,093,608 and 7,178,739, Taylor et al., U.S. published application US 2012/0298208 A1, and McKeague, U.S. Pat. No. 8,733,390. Somewhat similar systems have been used for monitoring and flushing ground water sources, as shown for example in Granato et al, U.S. Pat. No. 6,021,664. All of the patents and patent publications mentioned herein are hereby incorporated by reference.
Automatic flushing valves can be controlled by simple timers, or they can be controlled by complex computers such as programmable logic controllers (PLCs), which may in turn be internally programmed or may be controlled through a supervisory control and data acquisition (SCADA) interface. Such systems may periodically test for the concentration of chlorine (usually in the form of a hypochlorite salt), or for contaminants such as minerals, like lead or iron, or microbiological hazards, or for other characteristics of the water supply to which they are attached, and then activate flushing, alarms, water treatment, or other responses if these measures are out of specification.
Because automatic flushing valves are frequently located at a distance from an electrical power source, they are generally powered by batteries, and the batteries are recharged, if necessary, by a renewable source such as solar cells or a turbine run by the water being flushed.
Automatic flushing valves are frequently located in places subject to freezing temperatures. Because freezing water can damage the valve and its associated piping and controls, and because freezing temperatures may interfere with operation of the electronics associated with the valve, the valves in such situations are buried below the frost line or are placed in heavily insulated enclosures. Even such precautions, however, are not always sufficient to prevent damaging chilling of the valve and its associated controls and electronics. For example, in Granato et al, U.S. Pat. No. 6,021,664, Working Example Two, the system was twice shut down by freezing.